The present invention relates to the field of bus bar arrangements, and, more particularly, to a low inductance bus bar arrangement utilizing elongate bus bars vertically oriented and separated by one another with an insulating material.
From Bremer, et al., U.S. Pat. No. 4,809,153, a modular bus bar arrangement utilizing elongated vertically oriented bus bars separated by an insulating material therebetween is shown. The relationship between the inductance of the bus bar assembly and the orientation of the individual bars is taught to be proportional to the distance between the individual bars divided by the height of the bars. Therefore, it is suggested that the inductance of the bus bar assembly can be minimized by decreasing the distance between the individual bus bars and/or increasing the height of the bus bars. However, one problem with decreasing the inductance of the bus bar assembly by decreasing the distance between bars is that the propensity for arcing t between individual bars of different potential is greatly increased.
Bus bars of low inductance are commonly used in inverters operating at high switching frequencies and high power. A low inductance bus bar allows an inverter to operate reliably by reducing the propensity for voltage spikes and by reducing electromagnetic noise emanated by the bus bar. Moreover, low inductance bus bars reduce the likelihood that snubber circuits will be required on power modules for the bus bars.
In order to maintain a low inductance between the conductors of bus bars, the bus bars must be supported in a fixed position. However, the use of certain fastening means such as machine screws to support the conductors of the bus bars tends to create high electric field gradients which create points prone to dielectric failure in high and medium voltage applications. This dielectric failure could result in the destruction of the whole equipment.
It is also desireable to provide a system for connecting various electrical devices such as switching power modules to the bus bar assembly without increasing the inductance of the bus bar assembly and without creating regions of dielectric stress on the bus bar assembly and any connections thereto.
It is therefore an object of the present invention to provide a bus bar assembly which minimizes the inductance inherent therein without creating a situation where arcing between bus bars of different potential is facilitated.
It is also desireable to provide such a low inductance bus bar assembly which is capable of being connected to various electrical connections maintaining the dielectric integrity, as well as providing low inductance to the connected devices. Finally, the bus bar assembly should be able to provide the current carrying capabilities required, within the thermal and mechanical limits set by the materials and the equipment.